Short stature, Fanconi's anaemia, and risk of leukaemia after growth hormone therapy

Growth hormone supplementation increased latency to tumourigenesis in Atm-deficient mice

Growth hormone (GH) is important for cell growth and differentiation, has multiple effects on lymphoid tissue and may promote blast cell proliferation and cancer development. We studied the effect of GH on longevity and tumour formation in Atm-deficient mice, an established model of the human cancer prone syndrome ataxia telangiectasia (AT). AT is a devastating recessive disorder that is characterized by progressive cerebellar ataxia, immunodeficiency, chromosomal instability and cancer susceptibility. Since AT patients also show endocrinological abnormalities the question has been raised as to whether GH therapy could be beneficial and/or increase the cancer risk in AT. We found that treatment with GH significantly increased longevity of Atm-deficient mice. In addition, GH ameliorated locomotoric behaviour and improved T-cell immunity. Thus, our data demonstrated that GH treatment is not necessarily accompanied by increased cancer development in diseases with chromosomal instability and cancer susceptibility and might be beneficial for AT patients.

Improved growth velocity during thyroid hormone therapy in children with Fanconi anemia and borderline thyroid function

BACKGROUND

Children with Fanconi anemia (FA) tend to have short stature, mild thyrotropin (TSH) elevation, and borderline low free thyroxine (FT4). Objective was to examine whether thyroid hormone therapy improves linear growth in children with FA and borderline thyroid function tests

PROCEDURE

Thyroid function tests were performed in 63 children with FA. Eight subjects participated in a random order, double-blind, cross-over treatment for 7 months with levothyroxine and for 7 months with placebo. Monitoring included growth measurements and laboratory assays at 1, 4 and 7 months of each phase. A 1 month lead in/wash out period was excluded from analysis of each treatment phase.

RESULTS

The majority (63%) of FA children had borderline thyroid function tests. All eight FA subjects enrolled in the treatment study had FT4 in the lowest third of the normal range of 0.8-1.8 ng/dL (10.3-23.2 pmol/L) [FT4 0.9 +/- 0.1 ng/dL (mean +/- SD), range 0.8-1.2 ng/dL (10.3-15.4 pmol/L)]. TSH (optimal range 0.5-3 mU/L) was borderline elevated in six of eight subjects (4.0 +/- 1.5 mU/L, 1.9-7.3 mU/L). Growth velocity was slow at baseline and improved significantly during the thyroid phase compared to the placebo phase (2.1 +/- 1.2 cm/year vs. 5.4 +/- 1.7 cm/year, P < 0.05).

CONCLUSIONS

Thyroid hormone therapy is safe and may improve linear growth velocity in children with FA who have borderline thyroid function. Subtle hypothyroidism has importance for growth in children. Whether thyroid hormone treatment improves adult height in these children remains to be elucidated.

Factors and markers of growth hormone secretion and gonadal function in Fanconi anemia

Many factors may be involved in the growth and gonadal dysfunction of Fanconi anemia (FA).

OBJECTIVE

To evaluate the (1) relationship between FA presentation, including genital abnormalities and pituitary stalk interruption syndrome (PSIS), (2) markers of growth hormone (GH) deficiency and gonadal function, and (3) factors influencing final height and gonadal function.

PATIENTS

Twenty five patients with FA were included, 17 of them were given bone marrow transplantation.

RESULTS

Six patients were diagnosed with GH deficiency and PSIS (group A), whereas 19 had no evidence of GH deficiency (group B). In group A, all patients had more than 3 FA malformations and all 5 boys had cryptorchidism associated with microphallus in 4. All patients had heights and plasma insulin-like growth factor I < -3SD. Final height was reached in 15 patients and was < or = -2SD in 12 of them, all but 3 were born small for gestational age and/or given norethandrolone and/or corticosteroids. Gonadal function was abnormal in 5/7 boys and 4/5 girls evaluated at pubertal age. The plasma concentrations were low in 4/9 for antimüllerian hormone and in 3/9 for inhibin B, 3 of them had been given bone marrow transplantation.

CONCLUSIONS

PSIS can be part of a severe FA phenotype. It seems to occur mainly in boys, with more than 3 malformations, microphallus and cryptorchidism. This phenotype is associated with normal blood counts, defining a new clinical subgroup of patients.

Physiological and pathological growth hormone secretion

Growth hormone (GH) secretion is normally episodic, with discrete bursts of GH super-imposed on a minimal basal level of production. This pattern of GH production yields a dynamic state between a low baseline and intervening peaks, posing a challenge for the clinician attempting to understand the 'true GH status' in a specific patient. This pulsatile pattern is maintained throughout the day, but there are clear differences between different segments of the day, with approximately two-thirds of the total daily secretion produced at night. The dynamic nature of GH production has led many investigators to suggest that when evaluating short stature, parameters of spontaneous GH production be applied rather than the GH response to artificial stimulation. GH secretory patterns in healthy control populations are compared to those in patients with several conditions seen by the pediatric endocrinologist (classical GH deficiency, GH neurosecretory dysfunction, acute lymphoblastic leukemia, hypothyroidism, small for gestational age, Russell-Silver syndrome, constitutional delay of growth and puberty and Fanconi's anemia) and variables used for analysis of these patterns are described. Inferences made from comprehensive evaluations of the GH axis in Fanconi's anemia provide unique insight into general GH pathophysiology.

Evaluation of growth and hormonal status in patients referred to the International Fanconi Anemia Registry

OBJECTIVES

1) To determine the extent of short stature in patients with Fanconi anemia (FA); 2) to determine the extent and nature of endocrinopathy in FA; 3) to assess the impact on height of any endocrinopathies in these patients; and 4) to study the correlation, if any, between height, endocrinopathy, and FA complementation group.

STUDY DESIGN

Fifty-four patients with FA, 30 males and 24 females from 47 unrelated families, were prospectively evaluated in a Pediatric Clinical Research Center. The patients ranged in age from 0.1-31.9 years, with the mean age at assessment 8.6 years.

RESULTS

Endocrine abnormalities were found in 44 of the 54 FA patients tested (81%), including short stature, growth hormone (GH) insufficiency, hypothyroidism, glucose intolerance, hyperinsulinism, and/or overt diabetes mellitus. Twenty-one of 48 (44%) participants had a subnormal response to GH stimulation; 19 of 53 (36%) had overt or compensated hypothyroidism, while 8 of 40 participants had reduced thyroid-hormone binding. Two patients were diabetic at the time of study; impaired glucose tolerance was found in 8 of 40 patients (25%), but most surprisingly, hyperinsulinemia was present in 28 of 39 (72%) participants tested. Significantly, spontaneous overnight GH secretion was abnormal in all patients tested (n = 13). In addition, participants demonstrated a tendency toward primary hypothyroidism with serum tetraiodothyronine levels at the lower range of normal, while also having thyrotropin (thyroid-stimulating hormone) levels at the high end of normal. Sixteen patients were assigned to FA complementation group A, (FA-A), 12 to FA-C, and 5 to FA-G; 10 of the 12 participants in FA-C were homozygous for a mutation in the intron-4 donor splice site of the FANCC gene. Patients in groups FA-A and FA-G were relatively taller than the group as a whole (but still below the mean for the general population), whereas those in FA-C had a significantly reduced height for age. GH response to stimulation testing was most consistently normal in participants from FA-G, but this did not reach statistical significance. The tendency toward hypothyroidism was more pronounced in participants belonging to complementation groups FA-C and FA-G, whereas insulin resistance was most evident in patients in FA-G, and least evident in those in FA-C. Short stature was a very common finding among the patients with a mean height >2 standard deviations below the reference mean (standard deviation score: -2.35 +/- 0.28). Patients with subnormal GH response and those with overt or compensated hypothyroidism were shorter than the group with no endocrinopathies. The heights of those participants with glucose or insulin abnormalities were less severely affected than those of normoglycemic, normoinsulinemic participants, although all were significantly below the normal mean. The mean height standard deviation score of patients with entirely normal endocrine function was also >2 standard deviations below the normal mean, demonstrating that short stature is an inherent feature of FA.

CONCLUSION

Endocrinopathies are a common feature of FA, primarily manifesting as glucose/insulin abnormalities, GH insufficiency, and hypothyroidism. Although short stature is a well-recognized feature of FA, 23 patients (43%) were within 2 standard deviations, and 5 of these (9% of the total) were actually above the mean for height for the general population. Those patients with endocrine dysfunction are more likely to have short stature. These data indicate that short stature is an integral feature of FA, but that superimposed endocrinopathies further impact on growth. The demonstration of abnormal endogenous GH secretion may demonstrate an underlying hypothalamic-pituitary dysfunction that results in poor growth.

Growth hormone deficiency caused by pituitary stalk interruption in Fanconi's anemia

Fanconi's anemia can be associated with growth retardation. We describe biologic growth hormone deficiency, isolated or associated with thyrotropin abnormality, and pituitary stalk interruption syndrome on magnetic resonance imaging of 5 patients with Fanconi's anemia. Growth hormone treatment produced catch-up growth in all cases. These findings suggest a common genetic origin.

Growth hormone deficiency in one of two siblings with Fanconi's anaemia complementation group FA-D

Fanconi's anaemia (FA) shows great variability in phenotypic symptoms. We report on two FA siblings of German ancestry with the very rare form of the complementation group FA-D. Both presented with a similar phenotype and mild disease severity but with different growth. In the sister, growth velocity was normal, puberty and menarche occurred spontaneously. Her final height was within her parental target height. The younger brother had a reduced growth velocity, height SDS values below -5.5 SDS, a markedly retarded bone age, and delayed puberty. At the age of 12.9 years, growth hormone deficiency (GHD) was diagnosed and treatment with growth hormone was initiated. Our cases emphasize the heterogeneity of symptoms in FA even in siblings with the same genotype. In FA-children with severe growth retardation, GHD must also be considered.

Leukemia in children treated with growth hormone

An association between treatment with growth hormone (GH) and the development of leukemia was described in 1988. This perceived association is best explained by the fact that there are more children with GH deficiency (GHD) with risk factors predisposing them to leukemia than in the general population. These factors include previous cancers and their treatment, as well as co-existing conditions such as Down, Bloom and Fanconi syndromes. Examination of large databases of GH-treated individuals shows that GH-treated patients without these risk factors do not have an increased incidence of leukemia.

Relationship of growth hormone deficiency and leukemia

The use of growth hormone (GH) has been implicated as a possible risk factor for leukemia. We present data from six patients that support a working hypothesis that an increased risk of leukemia may exist in patients with GH deficiency not related to exogenous use of GH.